The invention described herein relates to nuclear reactor spent fuel storage pools and more particularly to an arrangement for providing on-site storage of all spent fuel rods removed from a reactor during its lifetime.
In the operation of conventional nuclear reactors used for generating electric power, the nuclear fuel becomes spent and must be removed at periodic intervals. Although refueling schedules vary, approximately one-third of the fuel assemblies must be removed annually so that replacement of all fuel assemblies in the core will take place over about a three-year period. Since nuclear reactors are designed for a life extending to approximately forty years, it is apparent that spent fuel storage facilities at the reactor site must accommodate about thirteen full cores of fuel assemblies, i.e., about twenty-six hundred fuel assemblies to accommodate all discharged fuel.
Currently, there is a dearth of fuel reprocessing facilities in the United States and throughout the world. Since the fuel reasonably cannot be reprocessed, the electric utilities who remove spent fuel assemblies from their nuclear reactors must provide for their safe storage so long as the fuel therein remains radioactive.
Historically, utilities have always provided fuel storage areas alongside the reactor to accommodate a small number of fuel assemblies. However, in view of the present uncertainties regarding reprocessing fuel and shipping spent fuel from the reactor site, utilities recently have taken positive steps to increase their on-site fuel storage capacities. As presently designed, the plant construction generally precludes increasing the actual size of spent fuel storage pools so other alternatives have been examined to determine how the storage capacity can be increased. As a result, an increase in capacity has been accomplished by locating fuel storage racks on a closer pitch in the spent fuel pool, to thereby increase the number of fuel storage racks in the available space. Although the fuel storage capacity is greater, present storage pools at most reactor sites will not accommodate all the fuel expected to be removed from a reactor over its lifetime, unless new structures or methods are developed. Since such space reasonably will not be available, an increase in spent fuel assemblies beyond that capable of being absorbed by the fuel pits could result in shutdown situations for particular reactor plants, and especially if off-site storage facilities also are not available. It therefore is apparent that the need exists for alternative structures and methods for storing spend fuel recovered from currently operating nuclear reactors.